PHP with PDO problem mysqli_stmt::fetch() [duplicate] - php

Question

This question already has answers here:
Can I mix MySQL APIs in PHP?
(4 answers)
Closed 2 years ago.
I need to convert my code to PDO and I don't know where is the problem.
$user = $_SESSION['user_email'];
$get_user = "SELECT * FROM users where user_email='$user'";
//This 2 lines was there in original
$run_user = mysqli_query($con,$get_user); //original
$row=mysqli_fetch_array($run_user); //original
//Converting to PDO
$run_user = $con->prepare($get_user);
$run_user->execute();
$row = $run_user->fetch(PDO::FETCH_ASSOC); //line 27
// line 38 and 39
$user_id = $row['user_id'];
$user_name = $row['user_name'];
My errors are:
Warning: mysqli_stmt::fetch() expects exactly 0 parameters, 1 given in
/Applications/XAMPP/xamppfiles/htdocs/network/includes/header.php on
line 27
Notice: Trying to access array offset on value of type null in
/Applications/XAMPP/xamppfiles/htdocs/network/includes/header.php on
line 38
Notice: Trying to access array offset on value of type null in
/Applications/XAMPP/xamppfiles/htdocs/network/includes/header.php on
line 39

Answer 1

To convert your code to PDO you must ensure that you connect with PDO first. These are two very different APIs and you can't mix them.
First connect:
$pdo = new PDO("mysql:host=localhost;dbname=test;charset=utf8mb4", 'user', 'pass', [
\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
\PDO::ATTR_EMULATE_PREPARES => false
]);
Then prepare and execute a statement. Pay attention to never include variables directly in SQL. Every piece of data should be bound separately. In your SQL, put ? where the data should be bound to, and then pass an array with values in execute()
$run_user = $pdo->prepare('SELECT * FROM users where user_email=?');
$run_user->execute([
$_SESSION['user_email']
]);
Now you can fetch the data. Make sure that your SQL actually fetched something before trying to access it.
$row = $run_user->fetch(PDO::FETCH_ASSOC);
if($row) {
$user_id = $row['user_id'];
$user_name = $row['user_name'];
}

Answer 2

You're mixing the mysqli and PDO interfaces. This isn't possible.
See this demo on how to do the same thing in PDO.
<?php
// Create a database using PDO, by passing a DSN (Data Source Name), username, and password.
// Replace yourserverhost, yourusername, yourpassword with the real credentials.
// Depending on the charset of your tables, you may want to change utf8mb4 as well,
// although this is a typical value.
$pdo = new PDO(
'mysql:host=yourserverhost;dbname=yourdatabasename;charset=utf8mb4',
'yourusername',
'yourpassword'
);
$user = $_SESSION['user_email'];
$sql = 'SELECT * FROM users where user_email=?';
$statement = $pdo->prepare($sql);
$statement->bindValue(1, $user, PDO::PARAM_STR);
$statement->execute();
$row = $statement->fetch(PDO::FETCH_ASSOC);
$user_id = $row['user_id'];
$user_name = $row['user_name'];
Your initial query is rewritten with a positional parameter (?).
The query is then made into a prepared statement to avoid SQL injection. The variable is bound using bindValue, starting at index 1. Other flavors of parameter binding are available.
PDOStatement::execute() runs the query.
PDOStatement::fetch(PDO::FETCH_ASSOC) fetches your row.
Do stuff with $row['user_id'] and $row['user_name'].